Madrid -LRB- CNN -RRB- -- Spanish rail chiefs testified on safety before lawmakers Thursday , two weeks after 79 people died and scores were injured in a horrific derailment in northwestern Spain .

The investigation has focused on the actions of the train 's driver , Francisco Jose Garzon , but questions have also been asked about the safety systems in place on Spain 's national railway network .

Gonzalo Ferre Molto , president of state-owned rail infrastructure company Adif , and Julio Gomez-Pomar , president of state railroad company Renfe , outlined what is being done to ensure the safety of rail travelers .

`` My desire is to know the whole truth and avoid the possibility of an event of this nature happening again , '' said Ferre . `` This is the best service we can offer to the victims and the whole Spanish society . ''

Lawmakers heard that the route the train was on , from Madrid to Ferrol , includes a mix of conventional and high-speed track , with the latter allowing high-speed trains to travel at over 200 kilometers per hour -LRB- 124 mph . -RRB-

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Two different safety systems are used in Spain : the European Rail Traffic Management System for the high-speed track and another known as ASFA on conventional lines .

The train and its engineer were switching between the two kinds of track and operating system in the course of the journey .

A transition from an ERTMS-operated section to the other system happened about four miles before the train derailed on a curve near the northwestern city of Santiago de Compostela , Ferre said .

That section of track had been inspected on April 20 , he said .

Speed limit on bend

Court officials have said the train was traveling at 153 kph -LRB- 95 mph -RRB- when it derailed , nearly twice the speed limit on the curve where the accident happened .

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After the accident , a temporary speed limit of 30 kph was imposed on the stretch where the accident occurred and is still in place , Ferre said . A permanent limit of 60 kph will come into force once that is lifted .

`` Our safety department is developing an investigation report , '' Ferre told the parliamentarians . `` Safety in the rail sector is an open subject . ''

Gomez-Pomar said Renfe has started to examine the safety systems in place and admitted that they can be improved .

He said the driver had taken control of the train at Ourense station at 8:06 p.m. , about 35 minutes before the crash occurred . Garzon had started his working day about eight hours earlier , but his effective driving time at that point was less than three hours , he said .

The driver , who has worked for Renfe since 1992 , had passed his most recent health test , Gomez-Pomar said . He had been qualified to travel the Ourense-Santiago stretch of track since February 2012 and was given permission to drive the kind of train involved in the crash last November .

In total , more than 7,000 trains have passed through the stretch where the accident occurred , Gomez-Pomar said .

Human error

Some lawmakers from smaller parliamentary groups criticized what they said was a rush to blame the driver for the crash .

`` Shifting the responsibility of a high-speed train on to the machine operator is , from our point of view , a rather excessive responsibility , '' said Rosana Perez , of the Mixed Group .

She suggested the number of drivers aboard a train should be increased as a safety measure to protect against human error .

`` It has been said that the only cause is the human factor . If it is really so , we are lost . This argument falls by its own weight , '' said Gaspar Llamazares , of the United Left group .

Charges filed

Investigations continue into the cause of the July 24 derailment , which shocked the nation .

As of Thursday , 38 people remain in the hospital , six of them -- all adults -- in critical condition , according to local health authorities . No nationalities were given for those still hospitalized .

Authorities have charged Garzon with 79 counts of homicide by professional recklessness and an undetermined number of counts of causing injury by professional recklessness . He has been given conditional release but has surrendered his passport .

Three witnesses were expected to give statements Thursday to a court in Galicia , in a closed-door session . They are a station manager and two neighbors who went to help the survivors immediately after the crash .

Minutes before the derailment , Garzon received a call on his work phone , apparently receiving instructions on the way to Ferrol from a Renfe staff member , a court in Galicia said last month .

The train was nearing the end of the six-hour trip between the capital and Ferrol at the time of the accident .

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CNN 's Laura Perez Maestro and Al Goodman reported from Madrid , and Laura Smith-Spark wrote in London .

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NEW : Minority party lawmakers say there 's a rush to pin blame on the train driver

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Rail chiefs say the train was traveling on a mix of conventional and high-speed track

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38 people remain in hospital two weeks after the train derailed in northwestern Spain

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Investigations continue into the cause of the deadly crash near Santiago de Compostela